Wafer-level manufacture of camera modules manufactured with CMOS technologies has contributed to the incorporation of camera modules in high-volume consumer products such as mobile devices and motor vehicles. FIG. 1 is a cross-sectional view of such a prior-art camera module 100 in an ambient medium 102. Camera module 100 includes a lens 172 having an optical axis 173 aligned with an image sensor 125, where a spacer ring 160 separates lens 172 and image sensor 125. Lens 172 and image sensor 125 are part of lens plate 170 and device layer 120 respectively. Solder balls 110 are electrically connected to image sensor 125. Solder balls 110, device layer 120, and cover glass 130 form a chip-scale package 135, which is also referred to herein as image sensor chip-scale package 135 and CSP 135. Spacer ring 160 and lens plate 170 form a lens unit 175.
In a process for manufacturing camera module 100, optical axis 173 is aligned to image sensor 125. Spacer ring 160 has a bottom surface 165 and CSP 135 has a CSP top surface 136. A glue ring 140 bonds spacer ring 160 to cover glass 130, between bottom surface 165 and CSP top surface 136, to form a cavity 148. A drawback of prior-art camera module 100 is that in the bonding process, spacer ring 160 deforms glue ring 140 such that portions of glue ring 140 exit regions between spacer ring 160 and cover glass 130. Upon curing, glue ring 140 may not completely seal, or securely seal, cavity 148 from ambient medium 102. For example, in camera module 100, a top surface 141 of glue ring 140 is separated from bottom surface 165(1). A broken seal between cavity 148 and ambient medium 102 risks contamination of at least one of lens 172 and cover glass 130. To eliminate this risk, camera module 100 includes extra edge glue 146 to secure the sealing of cavity 148. Application of extra edge glue 146 increases manufacturing costs associated with camera module 100.